


You Wanna Know?

by TellTaleKael



Series: Undertale Kinktober 2019 [5]
Category: Undertale (Video Game)
Genre: Bara Red, Grillby’s Food Will Go To Waste, LV Issues, M/M, PWP, Porn Without Plot, Red Has A Bad Day, Rough Sex, Sans Tries To Be Romantic, Size Difference, Smut, Sort Of, This Is Surprisingly Tame, Undertale Kinktober 2019
Language: English
Status: Completed
Published: 2019-10-08
Updated: 2019-10-08
Packaged: 2020-11-27 09:23:44
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,018
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20946044
Author URL: https://archiveofourown.org/users/TellTaleKael/pseuds/TellTaleKael
Summary: Undertale Kinktober 2019Day 5: Size Difference | Pairing: Red/SansRed had been stressed for weeks, so Sans decided to spend his day off putting together a little surprise for his mate.





	You Wanna Know?

**Author's Note:**

> I’ve fallen behind a few days, but I’m trying to catch up!

Sans flopped face-first on the couch with a groan, burying his face in the lumpy cushion. It had been one of his rare days off from work, and as much as he had wanted to use it to laze around, he had instead decided to be productive. The apartment would never be as spotless as his brother’s, but for an apartment shared by him and Red, it was practically like a new place. He’d put away the dishes that had been sitting in the dishwasher, vacuumed the random bits of chips and dirt from the living room carpet, washed all the laundry including the sheets to their bed, and had gone to pick up Grillby’s for supper. He’d even set up a cheap electric tea candle he’d bought from a dollar store on the table to make it more romantic.

Thing was, Red had been acting increasingly stressed for a few weeks. Sans hadn’t pushed too much, and Red hadn’t been forthcoming with any reason. But whatever it was, maybe a nice night in eating greasy food and rolling around in their fresh sheets would help. If it did, then even spending his day off to set it all up would be worth it.

He’d even changed from his usual shorts and jacket to some nicer jeans and the sweater Red had presented him with for his birthday, slightly big on him, but warm and soft and, most importantly, from Red.

Now Red just had to get home so Sans could pamper him.

He shifted on the couch to glance at the time on his phone. Red was a little later than usual, but he sometimes stayed behind to finish cleaning up, or stopped by the store on the way home to pick up something they were out of; like ketchup and mustard. He’d probably be home soon.

Sans’ sockets had just begun to drift low when he heard the unmistakable sound of the front door swinging open, followed by shuffling footsteps. He pushed himself up, peering over the back of the couch with a sleepy smile.

“hey babe. how was work?”

Red shuffled past the couch, shoulders hunched, not even looking at Sans. “don’t wanna talk about it,” he growled. He made his way up the stairs, wrenching the door to the bedroom opening. Frowning, Sans slipped off of the couch and followed him.

Red stood frozen in the doorway, staring at the freshly cleaned bed, the electric tea lights that sparkled around the room, and the little single-serve mustard packets that Sans had sprinkled around like cheesy, condiment-flavored rose petals leading to the bed.

“uh,” Sans said eloquently. He’d been planning on easing Red into their night together before bringing him up to the decked out room. The mustard packets had been to get a laugh out of him. Instead, Sans realized, Red’s broad shoulders began to shake with sobs. Immediately, Sans stepped around Red’s large form and took him by the hand to the bed, making him sit. “red, babe, what’s wrong?”

Red sniffled and wiped at his sockets. He didn’t look at Sans, staring down at the floor instead. “why d’ya even stay with me?” he asked. Sans inhaled lightly.

“because i love you,” he replied, forgoing any jokes for sincerity. Red’s expression twisted, and he scoffed.

“you could do better an’ we both know it.”

Sans climbed up and perched on Red’s lap, despite the latter’s protests. “‘better’ is a subjective term, but even if, hypothetically, i could ‘do better’, i wouldn’t want to. you’re the one i chose.”

Red looked frustrated at that, dragging his eyelights up to meet Sans’. “i could hurt ya.”

Well, that was new. Sans rested his hands on Red’s shoulders. “where did that come from? you aren’t going to hurt me.” He frowned. “what’s really going on?”

Red was quiet for a long moment, long enough that Sans almost spoke up again, but finally, “i was in the warehouse earlier ‘n something fell. just a fuckin’ box, but i nearly blasted the fool who dropped it. just so damn jumpy-“

“red,” Sans cut in, “your lv has been acting up, hasn’t it?” That would explain the way Red had been acting, tired yet antsy, mood swings, the stress... Sans hadn’t considered it because he thought they were past the point where Red hid this from him. The guilty silence from Red was all the confirmation he needed. “why didn’t you tell me?”

“thought i could handle it myself,” Red mumbled.

“bullshit,” Sans shot back. “even if you could, you know you don’t have to. we’ve been over this before.”

“ya shouldn’t have to deal with my bullshit-“

“i’m dealing with it now,” Sans interrupted. “i don’t have to, but i can choose to! you can’t take that choice from me,” he demanded hotly. Red stared at him, eyelights shrunk to pinpoints and... was that a flush on his face? “what?”

“you don’t even know what i wanna do to ya when i’m like this,” Red said. He brought his hands up, curling them around Sans’ sides. There was a guilt in his expression, even as he leaned into Sans’ space.

“no, i don’t. because you don’t tell me. if there’s something that can help, you gotta tell me.”

“you want me to tell you?”

“yes!”

Red chuckled dryly. “lv makes a monster crave violence. fighting ain’t the only violent action you can take. you wanna know how that applies here?” His eyelights burned as he said, “i wanna throw you down and rip those clothes offa ya. force ya up on your knees and ram my cock in that pretty little pussy you conjure for me, fuck ya until yer voice is hoarse from screaming and then fuck ya some more.” His phalanges tightened around Sans’ sides, before he forced himself to let go as if he had been burned. “that’s what i wanna do to ya. that’s why i don’t like coming to you when i’m like this.”

Sans slid off of Red’s lap, padding away from the bed. Red’s skull drooped, eyelights falling to the floor dejectedly. He didn’t look up as Sans stopped walking.

He finally did look up when the sweater came up over Sans’ head, and fluttered to the floor. “wh-what are you-?”

“okay,” Sans said.

“okay?”

“yeah. okay. except the ripping of the clothes, this is my favorite sweater. i’d be real _torn up_ if anything happened to it.” He unbuckled his jeans and began to shimmy them down. Red watched in alarm.

“sans, what? no, didja not hear what i just said?”

“i did. and i think you’re an idiot.”

“well, i ain’t contesting that but...” he grit his teeth when the jeans fell, leaving Sans standing there in the nude. “would you put yer clothes back on, i told ya I don’t want to hurt you.”

“and I told you that you aren’t going to hurt me,” Sans shot back. He padded back across the room, resting his hands on Red’s thighs. The telltale warmth of ecto below Red’s shorts told him that the other was already turned on. Sans rubbed small circles into the warmth. “i may have 1 hp but i’m not made of fucking glass, red. you know the intent isn’t there, so i can handle some roughness.” He climbed back up on Red’s lap, straddling his waist. “if it gets to be too much, i promise i’ll say something. we can even make a safeword if it’ll make you feel better.”

Sans summoned his ecto body. Soft, squishy stomach, curved thighs, a set of plump lips. He even went the extra mile and made a pair of heavy breasts, which he rarely summoned. They pressed against Red’s abdomen enticingly. “what do you say, huh?”

“hotcats. that’s the safeword.”

“okay, hotcats. got i-“

Sans’ words cut off with a startled groan as he was lifted and thrown down on the bed. He bounced lightly before Red settled over him, tongue lolling out. He gripped Sans’ jaw and kissed him deeply, forcing his tongue past Sans’ teeth and dominating his mouth. Sans groaned and summoned his own tongue, but struggled to keep up with the all-consuming, possessive kiss.

Red pulled back, leaving Sans panting as small, biting kisses were trailed down his body. There was the tiniest bite to his soft abdomen, before Red yanked his legs apart and dove down. The first sloppy, rough swipe of that broad tongue against his pussy made him fist his phalanges in the sheets. Red wasted no time, licking inside and working Sans’ inner walls, magic quickly coating his chin.

The difference was astounding. Red was always attentive and thorough, but he’d always been gentle. Sans appreciated it, but this... this was a whole different experience. A single thumb pressed against his clit and he cried out, legs tightening around Red’s skull as a surprise orgasm hit him. His entire body trembled with it, chest heaving and breasts bouncing.

“holy fuck,” he breathed. He whined when Red sat back on his haunches, licking the magic from his teeth with purpose. He made grabby hands at Red, but his mate had other ideas. He scooped Sans up and deposited him on his front, propped on his knees with his skull pressed to the mattress. He didn’t notice Red rid himself of his shorts, but he certainly felt the head of Red’s cock slip inside of him. Eased along by the slick of Sans’ orgasm, Red thrust into him, bottoming out in one movement.

“red!” Sans cried out, arching his back. Red curled over him, completely covering his body with his bulky frame, as if cocooning him from the world. Little kisses rained down across Sans’ shoulders, and one of Red’s hands slipped around to cup a breast, massaging lightly.

“fuckin’ beautiful,” Red murmured. He nibbled on the area he had been kissing, slowly pulling out, only to thrust back in. “too damn good fer me.” Before Sans could protest, he began to roll his hips in a quick rhythm. Soon, the sound of their ecto slapping together filled the room, harmonized with the moans that fell from their teeth. Sans could do no more than grasp at the sheets and take every rough, deep thrust. Red leaked magic into him, making the glide smoother and smoother until nothing but the stretch and pleasure were left.

Sans bit the pillow to try and stifle his cries, but Red yanked it away. “wanna hear ya.” He gripped Sans’ hips and pulled him back to meet each thrust. “wanna hear ya scream for me. make sure everyone knows who ya belong to. ya sing so sweetly.”

And scream Sans did. Red’s cock hit every sweet, sensitive spot inside of him on each thrust, and soon Sans was a drooling, writhing mess. He dug his phalanges into the bedding, trying to find any purchase. His second orgasm approached quickly, and before he could even scream out a warning, he clamped down on Red and came with blinding force.

And still Red fucked into him.

Sans’ body fell forward, loose and pliant. Red used this to his advantage, thrusting sloppily, chasing his own pleasure. Sans tried to clench down on him to help, but he felt loose-limbed and numb. Finally, Red gave one last mighty thrust and came with a roar, spilling into Sans in a flood that lasted for what felt like forever. Sans groaned weakly as he was filled to the point of Red’s magic shining through his own. His stomach felt heavy by the time Red carefully pulled out of him and helped him over onto his side.

Red flopped down next to Sans, large arms curling around him and pulling him up against Red’s chest. He rested a hand on Sans’ hip, lightly stroking with his thumb. They both laid there, panting, for a moment.

“how are ya doing, sweetheart?” Red asked eventually. Sans chuckled tiredly.

“_fucking_ great,” he said with a grin, snuggling closer to Red. He’d be sore, but damn was it worth it.

“so you’re ready for another round?”


End file.
